Monte Carlo simulation of gamma-ray interactions in an over-square high-purity germanium detector for in-vivo measurements

The developments of high-purity germanium detectors match very well the requirements of the in-vivo human body measurements regarding the gamma energy ranges of the radionuclides intended to be measured, the shape of the extended radioactive sources, and the measurement geometries. The Whole Body Co...

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Bibliographic Details
Main Author: Saizu, Mirela Angela
Format: Conference Proceeding
Language:English
Subjects:
Calibration
Cesium 137
Cesium isotopes
Collimation
Computer simulation
Efficiency
Gamma rays
Mathematical models
Modeling and Simulations
Monte Carlo simulation
Purity
Radiation shielding
Radiation transport
Radioisotopes
Sensors
Thickness
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Summary:The developments of high-purity germanium detectors match very well the requirements of the in-vivo human body measurements regarding the gamma energy ranges of the radionuclides intended to be measured, the shape of the extended radioactive sources, and the measurement geometries. The Whole Body Counter (WBC) from IFIN-HH is based on an “over-square” high-purity germanium detector (HPGe) to perform accurate measurements of the incorporated radionuclides emitting X and gamma rays in the energy range of 10 keV–1500 keV, under conditions of good shielding, suitable collimation, and calibration. As an alternative to the experimental efficiency calibration method consisting of using reference calibration sources with gamma energy lines that cover all the considered energy range, it is proposed to use the Monte Carlo method for the efficiency calibration of the WBC using the radiation transport code MCNP5. The HPGe detector was modelled and the gamma energy lines of 2 4 1 Am, 5 7 Co, 1 3 3 Ba, 1 3 7 Cs, 6 0 Co, and 1 5 2 Eu were simulated in order to obtain the virtual efficiency calibration curve of the WBC. The Monte Carlo method was validated by comparing the simulated results with the experimental measurements using point-like sources. For their optimum matching, the impact of the variation of the front dead layer thickness and of the detector photon absorbing layers materials on the HPGe detector efficiency was studied, and the detector’s model was refined. In order to perform the WBC efficiency calibration for realistic people monitoring, more numerical calculations were generated simulating extended sources of specific shape according to the standard man characteristics.
ISSN:2010-1945
2010-1945
DOI:10.1142/S2010194516602258